1. Field of Invention
The present invention relates to telescopic handwriting pens for PDAs (personal digital assistants) or cellular phones and more particularly to such a telescopic handwriting pen with improved characteristics.
2. Related Art
A conventional telescopic handwriting pen is shown in FIG. 5 and comprises first, second, and third sections 90, 91, and 92 in the form of sleeve. The first section 90 comprises a separate forward writing head 900 and has a rear end connected to a front end of the second section 91. A rear end of the second section 91 is connected to a front end of the third section 92. A rear end of the third section 92 is fitted with a cap 93. In use, pull the cap 93, the second section 91, and the third section 92 sequentially to form a pen. Two pairs of opposite, thin metal members 94 of arcuate section are provided between the first section 90 and the second section 91 and between the second section 91 and the third section 92 respectively. The section of each metal member 94 has an arc length less than half of periphery of the section 91 or 92 therebetween. The metal member 94 comprises a tab 95 on an inner surface. Correspondingly, two opposite holes 96 are formed on the front end of each of the second section 91 and the third section 92. The tabs 95 are snugly fitted in the holes 96 for fastening the metal members 94. Further, the metal members 94 provide a frictional contact either between the first and the second sections 90 and 91 or between the second and the third sections 91 and 92. As a result, the first, second, and third sections 90, 91, and 92 are prevented from disengaging the pen while outward sliding.
But this is unsatisfactory for the purpose for which the invention is concerned for the following reasons: First, loud sounds are produced in sliding operation of the pen sections due to contact with the metal members 94. Second, the sliding operation is not smooth due to no lubricating oil in the components of the pen. Third, the assembly is relatively difficult and time consuming. Particularly, fitting the tabs 95 in the holes 96 requires high precision with high manufacturing cost. Thus, it is not desirable in view of the competitive market.
Another conventional telescopic handwriting pen is shown in FIG. 6 and comprises an outer section 101 in the form of sleeve, an intermediate section 102 in the form of sleeve, and a solid, cylindrical inner section 103. The inner section 103 comprises at its front end an enlarged first coupling member 131 adapted to slide within the outer section 101, and at its rear end a second coupling member 132 adapted to slide within the intermediate section 102. In a fully extended state of the pen, the first coupling member 131 is blocked in the rear end of the outer section 101 and the second coupling member 132 is blocked in a front end of the intermediate section 102. To the contrary in a fully retracted state of the pen, the inner section 103 slides inside the intermediate section 102 and the intermediate section 102 slides inside the outer section 101 respectively.
But this is still unsatisfactory for the purpose for which the invention is concerned for the following reasons: First, the sliding operation is not smooth due to the solid inner section 103. Second, weight of the extended pen is not balanced because the inner section 103 is solid. As a result, inconvenience can be caused in a handwriting operation. Thus, the need for improvement still exists.